Fusarium wilt was reported to cause serious loss in the cultivated hemp crop Cannabis sativa in Italy (Noviello and Snyder, 1962). Due to its restricted host range this pathogen was proposed as a potential biocontrol agent for unwanted C. sativa (McCain and Noviello, 1984). Although this species shows promise as a biocontrol candidate, significant problems with effectively inoculating target species have been encountered by Fusarium researchers (Kraft and Haglund, 1978; Armstrong and Armstrong, 1981). In addition, these pathogens can be sensitive to numerous environmental factors, such as temperature, relative humidity, rainfall, etc.
Improving the delivery of the pathogen to the target plant could increase the kill rate of the mycoherbicide. Downward movement of the mycoherbicide from the soil surface into the rhizosphere limits the success of soil-borne biocontrol agents. To overcome these limitations, we evaluated the effectiveness of using live plant seeds coated with fungal spores as a delivery system for the mycoherbicide. Fusarium oxysporum f. sp. cannabis is nonpathogenic on plant species other than Cannabis. However, the pathogen will successfully grow on the root surface of nonhost plant as a saprophyte. Thus, as non-host seed coated with F. oxysporum f. sp. cannabis germinates and sends roots into the soil, the Fusarium multiplies, continues to colonize emerging tissue, and is carried further into the soil. This root growth effectively distributes the fungus through the soil environment, where it can contact the target host tissue and cause disease. An added benefit of live seed formulations, besides their ability to effectively deliver pathogens, is the ability to introduce a reclamation plant species as part of the treatment.